Hayrettin Ahlatci

Effect of Ti on the Corrosion Behaviour of In Situ Mg2Si Particle Reinforced Al–12Si-20Mg-XTi Alloys

In this study, corrosion behaviour of Al–12Si-20Mg-XTi alloys (Ti content varied between 0 and 4 wt.%) was investigated. Characterizations of the alloys were carried out by microstructural examinations and corrosion tests. Microstructural results showed that precipitation of the Mg2Si phases was observed in Al-12Si-20Mg-XTi alloy matrix as two different morphologies; i.e. as a polyhedral primary particle and as a chinese script. Upon addition of Ti, Al3Ti intermetallic precipitated in the alloy. Corrosion tests were carried out by immersing the alloys in “30 g/l NaCl+10 ml/l HCl” solution. Evaluation of corrosion was determined by measuring weight loss for 24 hours and by potentiodynamic polarization tests. Corrosion resistance of the alloy was approximately constant with 1 wt % Ti addition whereas at higher additions, the corrosion rate increased.

Characterization and Reduction Behavior of Cold-Bonded Composite Pellets for Direct Reduction Using an Organic Binder

The purpose of this study was to investigate the reduction behavior of cold-bonded composite pellets produced from low-grade hematite iron ore using molasses solution at various concentrations, as well as their physical and chemical properties. Direct-Reduction Iron (DRI) technology makes it possible to assess low-grade iron ores and convert them into scrap at facilities that have electric arc furnaces. The reductant used was coke with fixed carbon of 86.04%. The alkalinity rate was adjusted to 0.7 by adding calcium carbonate. In the composite pellets produced, the 300 N/pellet compression strength recommended in the literature was achieved with a Fetot/Cfix ratio of 2.5 and 3 using a 50% concentrated molasses solution. Composite pellets prepared with a Fetot/Cfix ratio of 3.5 using a 40% concentrated molasses solution reached a compression strength of 496 N/pellet. The porosity is inversely proportional to the increase in compression strength and binder concentration. Reduction experiments were conducted by applying different temperatures and durations to samples possessing optimum conditions for each Fetot/Cfix ratio: the best result was achieved with a 88% reduction rate in composite pellets with a Fetot/Cfix ratio of 3.5 at the end of 1 h. Pig iron nuggets were characterized using an optical microscopy (LOM) and a scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS).

Mechanical Properties of Pattern Welded 1075-15N20 Steels*

Abstract Forged welded (damascus) steels are produced by traditional methods and mostly used in the design of decorative tools. These steels are well-known for their good mechanical properties. The process for making forged welded (damascus) steel consists of stacking alternating sheets of different kinds of steel on top of each other and then forge welding them together. In this study, the steels 1075 and 15N20 were used for the forging and folding procedure. The effect of fold numbers on the microstructure and mechanical behavior were investigated. The steel consisted of both materials, 54 and 250 layers, respectively, produced by forge welding. The pattern layers are homogeneous and regular, but after the process sections with up to 54 pattern layers were irregular. Steel 1075 has a pearlitic microstructure, while steel 15N20 has a ferritic microstructure. The impact toughness and tensile strength of the folded steels improved with increasing the number of folds.

An investigation on dry sliding wear behaviour of pressure infiltrated AA1050-XMg/B4C composites

Abstract In this study, the effect of Mg alloying addition (1–4 wt.%) on dry sliding wear behaviour of AA1050 matrix composites was investigated. Composites were produced by the pressure infiltration technique at 800°C and had a B4C particle volume fraction of 60%. Reinforcement particles were uniformly distributed in the aluminium matrix. Compared with the AA1050 matrix, the weight loss of the composites decreased with increasing Mg content. The wear rate of the composites increased when the applied load and sliding distance were increased. The results show that when the applied load reaches critical values (30 N), the weight loss increases significantly.

The effect of head hardening process on the residual stress of rails

In this study, the head hardening process was employed, by using a mixture of air and water under laboratory conditions, to improve the residual stress behavior of R260 grade rails . For this purpose, three types of specimens were selected. One group of rails was heated up to the austenite stage and then cooled for 20 s; the next group was heated up to the austenite stage and then cooled for 40 s and the third group was not exposed to any heat treatment. The hardness results showed that the specimens cooled for 40 s had excessive hardness; the specimens cooled for 20 s exhibited similar properties as that of R350HT rail standards, which are especially preferred in the lower radius of curvature bends in railways, but not that of R260. According to the analysis of residual stress, all samples had compressive residual stress, but the specimens cooled for 20 s had the highest stress value.

Microstructure and corrosion properties of lanthanum-added AZ31 Mg alloys

In this study, the effect of lanthanum (La) on microstructure and corrosion properties of hot-rolled AZ31 Mg alloys was investigated. Light optical microscopy, scanning electron microscopy, and X-ray diffraction were applied for microstructure analysis. Potentiodynamic corrosion and immersion tests were being tried to assess the La effect on corrosion behavior. Moreover, how the rolling parameters and surface smoothness were changed of the corrosion rate was evaluated. Corrosion performance was developed by adding La and the corrosion rate was changed with the rolling speed.

Effect of Zn and Mn Additions on the Wear Resistance of Cast Alloy Mg – 5% Al – 1% Si

The effect of additions of Zn and Mn (from 0.5 to 4%) on the microstructure of alloy Mg – 5% Al – 1% Si is studied by the methods of x-ray diffractometry and light and scanning electron microscopy. The strength parameters are determined in tensile and wear tests. It is shown that particles of Mg2Si precipitate in the matrix and particles of Mg17Al12 precipitate on grain boundaries upon the introduction of low contents of Zn and Mn. Phases MgZn and Al6Mn precipitate at a high content of the additions. An optimum concentration of Zn and Mn is chosen for raising the wear resistance of alloy Mg – 5% Al – 1% Si.

Effect of Sn Addition on Corrosion Properties of As-Cast and Hot-Rolled AZ31 Magnesium Alloys

This study investigates the effect of Ti addition (0, 0.2, 0.5, 1wt%) on corrosion resistance of as-cast and hot rolled AM60 magnesium alloy. Corrosion behaviors were investigated by immersion tests and electrochemical analysis. The results showed that Ti addition altered the microstructure of as-cast AM60 magnesium alloy by decreasing the amount of β-Mg17Al12 eutectic phase. Homogenization treatment resulted in the dissolution of the most of the β-Mg17Al12 phases. Homogenized samples exhibited the lowest corrosion rate in immersion test while the best corrosion resistance was found for hot-rolled samples in electrochemical test. In hot-rolled state, Ti addition led to a slight change in the corrosion resistance of AM60 magnesium alloy.

Microstructure and Corrosion Properties of Homogenized Mg-4Zn-1La Magnesium Alloy

In this study, microstructure and corrosion behaviour of homogenized Mg-4Zn-1La magnesium alloy was investigated. Mg-4Zn-1La alloy was produced by low-pressure die casting method. Homogenization treatments were performed at 350 °C and 400 °C for 12, 18, 24 and 48 hours, followed by rapid cooling in water at room temperature. Microstructure characterizations showed that La addition led to a formation of semi-continuous network structure and islands of second phases which identified as T-phase (Mg7Zn3RE). A significant amount of second phase dissolution and an increase in a-Mg grain size with increasing both homogenization time and temperature was observed. Homogenization treatment led to an improvement in corrosion resistance of Mg-4Zn-1La alloy. Homogenization at 400 °C resulted in better corrosion resistance than homogenization at 350 °C for all homogenization duration.

Microstructure and Corrosion Properties of Homogenized AZ31 and AZ31+1%La Magnesium Alloys

Energy efficiency and decreasing emission of greenhouse gasses emerge that the importance of Mg alloys. Mg alloys can begin to supersede the steel and aluminum for structural applications, thanks to the developing of mechanical properties or corrosion resistance of Mg alloys. Rare earth metals such as Gd, Ce, Y and Nd have been utilized at AZ31 Mg alloys for this purpose in recent years. In this study, the effects of La addition and homogenization heat treatment on microstructure, hardness properties and corrosion resistance of AZ31 and modified AZ31 Mg alloys produced by low pressure die casting method were investigated.